In an instrument panel of a type with an integral airbag door, which is illustrated in the below-cited Patent Document 1, a cross-sectional shape of a door main body portion (i.e., a portion that excludes strut portions) of an airbag lid (an airbag door) as viewed in a vehicle front-and-rear direction is formed in a recessed shape that curves so as to recess toward the lower side. An “H”-shaped tear line portion (a portion intended to split open) is formed in the door main body portion. Thus, the front and rear of the airbag door (door portions) are formed to be partitioned. In addition, a pair of front and rear hinge line portions are formed at the door main body portion. This door main body portion is subject to inflation pressure of an airbag and the intended splitting portion splits open. Hence, the front and rear door portions open up to a vehicle cabin side thereof about the pair of hinge line portions. These hinge line portions curve in accordance with the curved shape of the door main body portion. The door main body portion is formed with a greatly reduced thickness at a central portion that excludes two end portions of the hinge line portions, and the two end portions of the hinge line portions are formed as increased thickness portions. Thus, a large splitting resistance (opening resistance) of the door portions when the airbag is inflating and expanding is avoided.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2003-200804